Electronic Toll Collection (ETC) systems enable drivers to pay road tolls without stopping their vehicles. An ETC system is especially useful for highways, bridges and tunnels with heavy traffic.
A Road Side Unit (RSU) broadcasts wireless signals at a certain frequency, such as 14 KHz square waves modulated by 5.83 GHz or 5.84 GHz carrier waves according to a standard (e.g., national standard of China).
An On Board Unit (OBU) uses a wake-up circuit, which will wake up the primary circuit in the OBU when one or more preset conditions are met. However, power consumption of existing wake-up circuits is too high, which is a main factor in restricting extension and application thereof.
Therefore, it is desirable to develop a new wake-up circuit with lower power consumption that can be used in OBUs.